Abstract
Engineering conducting polymer thin films with morphological homogeneity and long-range molecular ordering is intriguing to achieve high-performance organic electronics. Polyaniline (PANI) has attracted considerable interest due to its appealing electrical conductivity and diverse chemistry. However, the synthesis of large-area PANI thin film and the control of its crystallinity and thickness remain challenging because of the complex intermolecular interactions of aniline oligomers. Here we report a facile route combining air-water interface and surfactant monolayer as templates to synthesize crystalline quasi-two-dimensional (q2D) PANI with lateral size ~50 cm2 and tunable thickness (2.6–30 nm). The achieved q2D PANI exhibits anisotropic charge transport and a lateral conductivity up to 160 S cm−1 doped by hydrogen chloride (HCl). Moreover, the q2D PANI displays superior chemiresistive sensing toward ammonia (30 ppb), and volatile organic compounds (10 ppm). Our work highlights the q2D PANI as promising electroactive materials for thin-film organic electronics.
Highlights
Engineering conducting polymer thin films with morphological homogeneity and long-range molecular ordering is intriguing to achieve high-performance organic electronics
The q2D PANI film was synthesized via the oxidative polymerization of aniline monomers at the airwater interface with the assistance of a surfactant monolayer
Reproducible selected area electron diffraction (SAED) patterns have been observed from the freestanding q2D PANI thin film (~9.3 nm thick; Fig. 3a and Supplementary Fig. 6), demonstrating its excellent crystallinity
Summary
Engineering conducting polymer thin films with morphological homogeneity and long-range molecular ordering is intriguing to achieve high-performance organic electronics. To achieve long-range charge transport, one promising strategy is to align the linear conducting polymer chains into quasi-two-dimensional (q2D) crystalline films[10,11]. Vigorous effort has been devoted to fabricating PANI thin films, including (i) top-down solution processing of PANI chains via spin coating[20], drop casting[21], and Langmuir-Blodgett technology[22], and (ii) bottomup synthesis from monomers via self-assembled monolayer (SAM) templating[23], chemical vapor deposition[24,25], and air (or liquid)-liquid interfacial method[26,27] These strategies only produced inhomogeneous and amorphous (i.e., randomly compact-coil conformation) PANI films or partially crystalline nanofiber-, rod- and sphere-shaped PANIs21,22,26, due to the poor processability of PANIs and complex intermolecular interactions of aniline/oligomers[28]. The ultra-thinness in conjunction with high crystallinity render q2D PANIs high-performance electrode materials for chemiresistive sensors, enabling sensitive detection of ammonia gas down to 30 ppb and volatile organic compounds (e.g., heptanal) at 10 ppm
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